whole wheat bread vs dark bread

whole wheat bread and dark bread both are nouns.

Word	Noun	Adjective	Verb	Adverb
whole wheat bread	Yes	No	No	No
dark bread	Yes	No	No	No

As nouns, whole wheat bread and dark bread are synonyms defined as:

Other synonyms of whole wheat bread include brown bread, whole meal bread.

whole wheat bread (noun)	dark bread (noun)
bread made with whole wheat flour	bread made with whole wheat flour